Patent U.S. Pat. No. 4,318,557 has already disclosed the production of a latch joining two parts and comprising a hook possessing a curved end capable of engaging with a retaining member connected to the first part, an operating member pivoting about an end pin situated at the opposite end from the curved end of the hook, and an articulation divided, on the one hand, into a first pair of compression links pivoting on a main pin designed to be attached firmly to the second part and on an intermediate pin, the latter being positioned between the main pin and the end pin, and, on the other hand, into a second pair of compression links pivoting on said intermediate pin and on the end pin. In such a latch, the static main pin is located between the operating member and the hook, and supports the latter. Generally speaking, such a latch is installed on the underside of an airplane structure, operating member downmost. The kinematics of the latch and the gravity applied to the various parts of the latch therefore contribute to the hook coming away from the retaining member. However, during the phase of opening, in accordance with the balance of the hook on the one hand and the operating member on the other, the curved end of the hook may remain in contact with the retaining member and cause an undesired rotation of the hook about said retaining member. In such a situation, further opening is not permitted in order to prevent damage to the structure or to the latch itself.
To reduce this risk, it is possible for example to place a weight on the curved end of the hook to ensure a sufficient separation of the hook and operating member away from the retaining member when opening the latch. However, such an arrangement has a significant impact on the mass, size and reliability of the latch.
European patent application EP 0 431 769 discloses a latch of the same type comprising a hook containing an elongate closed hole carrying the main pin. The sides of this hole constitute bearing surfaces to limit lateral movement of the hook on the main pin. Such a latch is smaller than the latch according to U.S. Pat. No. 4,318,557, but it is again necessary to employ additional means, such as a weight, to help the hook to move sufficiently away from the retaining member as the latched is opened.